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© Stock.Adobe.com/au/Hoda Bogdan

research and development

or at or y/R ice Univ ersity.

Programmable cement particles

Im ab ag ls L ec ria our ate tesy M of the Multiscale

create stronger structures US scientists have decoded the kinetic properties of cement and developed a way to ‘program’ the microscopic, semicrystalline particles within.

D

eveloped at Rice University

the final particles. Decreasing the calcium

and published in the Journal

silicate yielded more spherical particles

of Materials Chemistry A,

and smaller cubes, while increasing it

the process turns particles

formed clumped spheres and interlock-

from disordered clumps into

ing cubes.

regimented cubes, spheres and other forms

“The seed particles form first, auto-

that combine to make the material less

matically, in our reactions, and then they

porous and more durable. The technique

dominate the process as the rest of the

may lead to stronger structures that re-

material forms around them,” Shahsavari

quire less concrete, making them more

said. “That’s the beauty of it. It’s in situ,

environmentally friendly. Lead author Rouzbeh Shahsavari and

An isolated cement cube created by the lab of Rouzbeh Shahsavari. Image courtesy of the Multiscale Materials Laboratory/Rice University.

seed-mediated growth and does not require external addition of seed particles, as

his colleagues decoded the nanoscale

surfactants and calcium silicate to C-S-H

commonly done in the industry to promote

reactions — or ‘morphogenesis’ — of the

and exposing the mix to carbon dioxide

crystallisation and growth.”

crystallisation within calcium-silicate hy-

and ultrasonic sound. The crystal seeds

The new technique has several envi-

drate (C-S-H) cement that holds concrete

took shape around surfactant micelles

ronmental benefits, Shahsavari said. “One

together. Previous techniques to create

within 25 min.

is that you need less of it [the concrete]

ordered crystals in C-S-H had required

Once the calcite seeds formed, they

because it is stronger. This stems from

high temperatures or pressures, prolonged

triggered the molecules around them to

better packing of the cubic particles,

reaction times and the use of organic

self-assemble into various shapes that

which leads to stronger microstructures.

precursors, but none were efficient or

can pack more tightly together in con-

The other is that it will be more durable.

environmentally benign.

crete than amorphous particles. Carefully

Less porosity makes it harder for un-

The Rice researchers created their

modulating the precursor concentration,

wanted chemicals to find a path through

cubes and rectangles by adding small

temperature and duration of the reaction

the concrete, so it does a better job of

amounts of positive or negative ionic

varied the yield, size and morphology of

protecting steel reinforcement inside.”

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Sustainability Matters is a bi-monthly magazine showcasing the latest products, technology and sustainable solutions for industry, governmen...